Lynn, Joanne, and Rick - Thank you!
Rick - I used a tube of construction adhesive to "glue" the cinder blocks and caps together. My yard slopes and erodes, so I had to adhere the cinder blocks together somehow to keep them from shifting. The two center garden squares are made from recycled plastic slates. I won't use wood here at all anymore. The slates were more expensive, but should also last a long time. They are flimsy compared to the cinder blocks but they sit on the top surface of each layer of bed without sinking down, which is good!
I've seen the 12" square paver idea, too. I had considered that as well, but I like the cinder blocks and caps because they are wider and serve double duty as a place to sit to weed or plant in the 3-tiered bed. I've tried all different ways to make garden beds and this has worked the best for me considering where I live, my sloping backyard, and the climate. The best part is how cheap the cinder blocks are! I don't think there is anything I could purchase cheaper. I know getting material free from a refuse or recycle company would be even better, but I did not have any luck pursuing that idea.
One thing to keep in mind if you make a small garden bed using cinder blocks is that the cinder blocks will leach lime into the soil against the blocks. So be aware of that fact. You could make the cinder block bed and then let it sit for a month or so during the rainy season before filling with soil to wash away some of the lime. Just a suggestion. So far, I have not had a problem with the lime at all. I have the spider plants growing in the holes of the cinder blocks with no apparent ill affect.
